A data digest is a data-integrity-checking value that is computed for a segment of digital data in a computer system. These digests (of which checksums are a special, common case) have proven useful for ensuring data integrity in transmission and storage of data. The digest is a mathematical function of the data, with the digest usually much smaller than the data segment to be protected. This data-integrity-checking value is often included with the original data when a message is transmitted or communicated, in space or time, to a data consumer. The consumer can compute the data digest for the data using the same digest scheme employed by the digest generator and then compare the value of the computed digest with the digest value received. If the two digest values match, then there is a high probability that the data was transmitted or stored without error. Note that as used in the description and any appended claims, the terms “digest” and “data-integrity-checking value” will have the same meaning.
In today's networked computing environments, the number of processors often found between data producers and consumers continues to increase. These processors may not be under the control of either the producer or the consumers of the data. Further, either the producer or the consumers of data may not know the integrity with which each processor manipulates or communicates data. For example, a communication network may be implemented according to the InfiniBand™ Architecture Specification developed by the InfiniBand Trade AssociationSM, the specification for which is incorporated herein by reference (InfiniBand™ Architecture Specification, version 1.0). The InfiniBand™ Architecture defines a system area network for connecting host processor nodes, input/output (“IO”) platforms, and IO devices, as is shown in FIG. 1. System 100 is a communications and management infrastructure supporting both IO and interprocessor communications for one or more computer systems. The system 100 can range from a small server with one processor and a few IO devices to a massively parallel supercomputer installation with hundreds of processors and thousands of IO devices. Communication among nodes is accomplished according to an InfiniBand™ protocol. In addition, the IP (Internet protocol) friendly nature of the architecture allows bridging to an Internet, intranet, or connection to remote computer systems 111.
The InfiniBand™ architecture defines a switched communications fabric 101 allowing many devices to concurrently communicate with high bandwidth and low latency in a protected, remotely managed environment. The system 100 consists of processor nodes 102, 103, and 104 and IO units 105, 106, 107, and 108 connected through the fabric 101. The fabric is made up of cascaded switches 109 and routers 110. IO units can range in complexity from a single attached device, such as a SCSI or LAN adapter to large memory rich RAID subsystems 107. While some InfiniBand™ transfers among nodes may be protected using data digests, the integrity of intra-node programming may not be guaranteed. In fact, the path that data will travel between data producers and consumers may vary due to adaptive routing procedures and the like. Thus, a mechanism is needed to verify the end-to-end integrity of a data transfer from an application that produces or manipulates data to one or more applications that use the data.